Mechanical system for manufacturing pigment-coated paper



Marh10,1970 Q E.BOHMER ETAL 3,499,419

KECHANICAL SYSTEM FOR MANUFACTURING PIGMENT-COATED PAPER Filed Dec. 20. 1967. 2 Sheets-Sheet 1 FIG].

March 10, 1970 E. BOHMER ETAL 3,499,419

MECHANICAL SYSTEM FOR MANUFACTURING PIGMENT-COATED PAPER Filed Dec. 20. 1967 2 Sheets-Sheet 2 Int. Cl. lisc 1/12 US. Cl. 118206 2 Claims ABSTRACT OF THE DISCLOSURE For the one or two side coating of a paper web, a device is provided comprising two spaced main rollers with an intermediate roll arranged therebetween. The intermediate roll is of a smaller diameter than the main rolls and intermediate roller is arranged so that the web passes through a nip between one of the main rollers and the inter-mediate roll. The web is led in contact with the intermediate roll over a part of the circumference of the latter after the web is passed through the nip, so that there is obtained an abruptly moving of the web from the surface of the main roll which the web makes contact. The intermediate roll is arranged for horizontal displacement on both sides of a center line between the main rolls in such a way that contact is maintained with the main rolls.

This invention deals with mechanical systems for manufacturing a paper coated on both sides. Several different principles have previously been suggested and actually used in paper mills, one of the simplest being the size press. The paper web in this press passes through a nip between two rolls, of which one is usually a steel roll and the other rubber covered. The lower roll may rotate in a tray of coating color, which is transferred by means of the roll to the bottom side of the paper. On the top side of the paper, the coating color may be sprayed either on the roll surface or directly on the paper web. The size press may also be arranged with a vertical run of the paper, or the rolls may be positioned at different angles between 0 and 90, the latter angles meaning that the rolls are stacked vertically above each other.

Experience has shown that the size press may give a satisfactory coated surface as long as the operating speed is low and the coating weight small. An increase of the speed or the viscosity of the coating color may give an effect called orange peel which is a great disadvantage during the subsequent printing process. This pattern is related to cavitation and viscoelastic phenomena occurring in the outgoing part of the nip, and the degree of this effect will increase when the cohesion of the coating color and consequently the viscosity is increased. The geometry of the roll nip is also important, and it is known that roll diameter and take-01f angle will influence the results.

An object of this invention is to provide an apparatus which will not produce the orange peel effect while operating at speeds and with coating weights and material theretofore unusable.

FIG. 1 is a side view of the preferred embodiment of the invention.

. United States Patent 0 3,499,419 Patented Mar. 10, 1970 FIG. 2 is a side view of a second embodiment of the invention.

Referring to FIG. 1, size rolls A and B are here arranged out of engagement and between them a further roll is situated, the further roll having a substantially smaller diameter than the two main rolls and preferably a diameter of 3-6", the paper web being led through the nip between one of the main rolls and the further roll. In this way, the paper web is removed more abruptly from the rolls. A small intermediate roll therefore is favorable only in such degree it is combined with a convenient guiding of the web when passing out of the nip. The web preferably follows the small intermediate roll, but the invention specifies no fixed exit angle and an alternative web direction is also illustrated in FIG. 1.

The intermediate roll C in the embodiment shown can be made from hard rubber, steel or other suitable material. The intermediate roll diameter r can vary between R/ 15 and R/ 13 (see FIG. 1) but preferably is between R/S and R/ 3. As mentioned above the diameter preferably is 3-6". The rolls A and B can be conventional size rolls as to material as well as diameter. The top roll may be grooved or smooth, and as example rolls with a diameter of 50 cm. may be mentioned, the one covered with hard rubber and the other made of steel, bronze or any other suitable material.

The intermediate roll must be horizontally displaceable on both sides of the nip depending on the speed, the Web direction and the composition of the coating mass. It is assumed that at all time there is physical contact between the intermediate roll C and the rolls A and B. As appears from FIG. 1, the rolls A and B rotate in the same direction and this is decided by the machine mounting. Roll C rotates in opposite direction.

We claim:

1. A device for coating both sides of a paper web, said device comprising two spaced main rolls of about the same size which are rotatable in the same direction, an inter-mediate roll of smaller diameter than the main rolls and rotatable in the opposite direction, said intermediate roll having a diameter between /3 and /s the diameter of the main rolls, said intermediate roll being arranged between the main rolls and in contact therewith so that the web passes through a nip between one of the main rolls and said intermediate roll, means whereby the web is led in contact with the intermediate roll over a part of the circumference of the latter after the web has passed through the nip, whereby there is obtained an abrupt removing of the web from the surface of the main roll with which the web makes contact, and means for applying a coating material onto both sides of the web before removal of the web from the surface of the main roll, the latter means comprising a vessel containing coating material, said main roll with which the web makes contact being immersed in said coating material in the vessel to apply coating material to one side of the web, and spray means for applying coating material to said web on the other side thereof at a location just prior to entry of the web into said nip.

2. A device according to claim 1 comprising means whereby the intermediate roll can be displaced horizontally on both sides of a center line between said main rolls such that contact is maintained between at least one of the main rolls and the intermediate roll.

(References on following page) References Cited UNITED STATES PATENTS Bradner 118206 Kirschbraun 1 18206 Kanitz 101153 Behringer.

Barrett et a1. 118249 Lutz 118249 XR 2,593,149 7 4/1952 Illner. 3,116,166 12/1963 Halley 118-249 XR WALTER A. SCHEEL, Primary Examiner 5 ROBERT L. SMITH, Assistant Examiner US. Cl. X.R. 1 18-249, 41 1 

